electrical wave height gages in the vicinity of where the toe of the test 

 sections was to be placed (without the structure in place) and recorded on 

 chart paper by an electrically operated oscillograph. The electrical output 

 of the wave gages was directly proportional to their submergence depth. 



Selection of Test Conditions 



14. Breaking wave tests were conducted using dolos overlays. A review 

 of past site-specific stability projects and hydrographic data showed that 

 typical prototype sea-bottom slopes could range from almost flat to as steep 

 as IV on lOH. Realizing that wave deformation and severity of breaking action 

 increases as bottom slope increases, and since time constraints would allow 

 testing of only one slope, it was decided to use a IV-on-lOH slope, thus 

 ensuring severe depth-limited breaking wave action (plunging breakers) . When 

 breaking directly on the structure, this type of wave normally causes the most 

 damage to rubble-mound structures. 



15. By nondimensionalizing design conditions from site-specific pro- 

 jects, it was found that a relative depth (d/L) range of 0.4 to 0.14 should 

 include most prototype conditions encountered in breaking wave stability 

 designs. A review of capabilities of the available flume and wave generator 

 showed that this range of d/L values could be achieved for a reasonable 

 range of testing depths. 



16. The wave flume was calibrated for depths from 0.40 to 1.00 ft in 

 0.05-ft increments at d/L values of 0.04, 0.06, 0.08, 0.10, 0.12, and 0.14. 

 This range of depths, and consequently breaking wave heights, proved to be 

 compatible with the selected armor weights and sea-side breakwater slopes. 



17. All stability tests were conducted on sections of the type shown in 

 Figure 1 and Photos 1-4. Sea-side slopes of IV on 1.5H and IV on 2H were in- 

 vestigated, while the beach-side slope was held constant at IV on 1.5H. 

 Heights of the simulated existing structures (prior to placement of the dolos 

 overlays) varied from 1.0 to 1.2 ft. The height necessary to prevent wave 

 overtopping of the existing structure was determined from the slopes, water 

 depths, and wave heights Investigated in determining stability coefficients 

 for the dissimilar armor overlays. 



18. It was assumed that the overlaying dolos armor could be slightly to 

 significantly smaller than the existing tribars. A review of existing model 



10 



